1. Field of the Invention
The present invention relates to a keyboard lid (fallboard), its open-close structure and arm members for keyed instrument such as an electronic piano.
2. Description of Background Art
Heretofore it is known a keyboard lid for keyed instrument, for example, as disclosed in Japanese Laid-open Utility Model Publication No. 8390/91. This keyboard lid comprises a lid body and frame plates arranged at before and behind ends of the lid body to decorate and reinforce it. The frame plates are integrally constructed as having a substantially H-shaped cross-section and assembled to the lid body with the ends of the lid body inserted into the inside of the frame plates. The upper half of the frame plates exposed to the outside of the instrument body is adapted to function mainly as a decoration member and the lower half of the frame plates concealed within the instrument body is adapted to function mainly as a reinforcing member.
However since the frame plate of the prior art has an integrally formed structure, there is a limitation in selecting materials such that whole structure can satisfy both the decorative and reinforcing functions. That is, when a material superior in decorative function such as wood is selected the frame plate must be thickened for reinforcement and reduces the space efficiency especially in the back side of the frame plate. On the other hand, when a material superior in strength such as steel is selected the decorative function is reduced. If using, for example, an extruded aluminum member to satisfy both the functions, the cost for forming the frame plate is increased.
Japanese Laid-open Utility Model Publication No. 8390/91 also discloses an open-close structure of a slide lid which is one of open-close structures of a keyboard lid for keyed instrument. The slide lid is so constructed that it can slide between a close position in which the lid is pulled out proximally to cover the keyboard and an open position in which the lid is pushed distally into the instrument body to expose the keyboard. Arranged at opposite sides of the keyboard are inner plates of arm member which extend into the instrument body. Each inner plate is provided with, at a proximal external side thereof, a decoration plate for supporting the slide lid in the close position and decorating the keyboard, and at an distal inside thereof, a rack and a guide groove for carrying out smooth sliding of the slide lid. These decoration plate, rack and guide groove are formed integrally with each other. A pair of right and left pinions mating with the rack is mounted on the distal end of the slide lid and the opposite ends of the pinion shaft are adapted to be guided within the guide groove. On opening and closing of the lid by a player, he grasps the lid with his fingers hooking the handle portion of the front bottom end of the lid, and then lifts up and pushes distally the lid to open it or pulls the lid proximally to close it. The slide lid is adapted to be slid in and out the instrument body through a slit formed between a control panel arranged behind the keyboard and a top plate.
However, since the slide lid of the prior art can be freely opened and closed at the proximal end thereof, it is often erroneusly over-lifted and therefore the upper surface of the lid is liable to abut against the top plate of the instrument body and thus damages the top plate or the slide lid. This is apt to be caused due to a fact that the conventional keyboard lid adopts a structure to open the lid by pulling the lid up and then falling it down distally and a fact that the lid is naturally lifted up when it is pulled up with fingers hooking the handle portion of the lid. In addition, it is hard to smoothly slide the lid when the direction on which the lid is arranged is out of the direction of the guide groove.
Japanese Laid-open Utility Model Publication No. 8390/91 further discloses arm members for a keyed instrument. Each of the arm members has an outer plate of arm member forming an upper surface, external side surfaces and front and rear surfaces of the arm member, an inner plate forming an inside side surface thereof, and a decoration plate arranged close to a keyboard and decorating it. These plates are formed of the same material as each other such as plastics and the inner plate and the decoration plate are integrally formed with one another. The inner plate with the decoration plate is secured to the outer plate by screws via a plurality of bosses projected from the inside surface of the outer plate.
Such conventional arm member must be so designed that it stands against heavy load since the arm member is heavy in its own weight and it has to support weights of persons or articles when they are leaned against or placed on it. On the other hand, the arm member must be superior in decoration since it is a very important element for the decoration of a keyed instrument. That is, the arm member must have both the decorative and reinforcing functions. However since the arm member of the prior art is formed by outer and inner plates of the same material, the arm member is apt to be weakened in strength when its material is selected from those taken serious view of decorative function, on the contrary, the arm member is apt to become poor in decoration when its material is selected from those taken view of reinforcing function. Also if the arm member is formed by a material satisfying both the functions, the degree of freedom of selection of material is decreased and the manufacturing cost of them is increased. In addition, since the inner plate of arm member except for the decoration plate is concealed within the instrument body, when the arm member is formed by a material taken serious view of decorative function this portion will result in costly vain.